1. Field of the Invention
The present invention relates to an optical information recording and reproducing apparatus for recording and reproducing information onto and from an optical record medium in a form of a tape or a card.
2. Description of the Related Art
There is an optical disk as a record medium for recording and reproducing an audio signal and an image signal. Although a high record density can be attained by the optical disk, an area which can be used for the recording operation is rather small. Thus, when considering a whole disk, there is a certain limit in a memory capacity thereof.
On the other hand, a record medium in a form of a tape, such as a magnetic tape used for VTR (Video Tape Recorder) and the like, is inferior in the record density to the optical disk. However, it is possible to record the information onto the record medium in the form of the tape, in the amount of approximately 100 times as much as that of the optical disk in respect of the record capacity.
Hence, a record medium, which is compact and has a large record capacity, can be attained by combining the high record density of the optical disk with the large record capacity of the record medium in the form of the tape.
Therefore, for example, it is researched to perform the recording or reproducing operation of the information by applying a laser light to the optical record medium in the form of the tape (hereafter, it is referred to as an "optical tape") in which a magneto-optical record film, such as TbFeCo and the like, is formed on a base film in the similar manner as in the magnetic tape
An optical record medium in the form of the card having the above mentioned magneto-optical record film as the optical record medium (hereafter, it is referred to as an "optical card") in the similar manner as in the optical tape is also researched. The optical card may be used in a particular field such as a management of a medical chart and the like.
FIG. 11 shows a schematic configuration of one example of an optical information recording and reproducing apparatus for recording and reproducing information onto and from the optical tape or the optical card in the above mentioned related art.
As shown in FIG. 11, an optical information recording and reproducing apparatus 100 is provided with: a signal processor 106 for signal-processing an external input signal Si to be recorded and then converting it into a record signal Sr to thereby output it to a stationary optical system 105, and further signal-processing a reproduction signal Sp from the stationary optical system 105 to externally output it as an output signal So; the stationary optical system 105, which has a light beam emitting device for emitting a light beam B (a light beam for recording) to record information onto an optical card 1 (or an optical tape) when recording the information, on the basis of the record signal Sr, and further emitting a light beam B (a light beam for reproducing) when reproducing the information, and also has a light receiving device for receiving a reflection light from the optical card 1 (or the optical tape) of the light beam B (the light beam for reproducing) when reproducing the information to thereby output the reproduction signal Sp; a rotatable optical system 104 for collecting on the optical card 1 (or the optical tape) the light beam B (the light beam for recording) emitted from the stationary optical system 105 when recording, and further guiding to the stationary optical system 105 the reflection light of the light beam B (the light beam for reproducing) from the optical card 1 (or the optical tape) when reproducing, while it is being rotated with a straight line perpendicular to a record surface of the optical card 1 (or the optical tape) as a central axis; and a magnet (not shown) for applying a magnetic field to the optical card 1 (or the optical tape) when recording and reproducing the information.
Among them, the rotatable optical system 104 is provided with: reflection mirrors 102 and 103 for forming an optical path of guiding to an objective lens 101 the light beam B (the light beam for recording) emitted from the stationary optical system 105 when recording, and further guiding to the stationary optical system 105 the reflection light of the light beam B (the light beam for reproducing) from the optical card 1 (or the optical tape) when reproducing; and the objective lens 101 for collecting on the record surface of the optical card 1 (or the optical tape) the light beam B. Then, the rotatable optical system 104 which integrates the reflection mirrors 102 and 103, and the objective lens 101 in one body, is rotated by a drive device (not shown) with the straight line perpendicular to the record surface of the optical card 1 (or the optical tape) as a rotational axis.
The information is recorded by the optical information recording and reproducing apparatus 100 having the above mentioned configuration when recording the information, while circular information tracks TR are being sequentially formed on the optical card 1 (or the optical tape). When reproducing the information, the information recorded on the information tracks TR is read out by the light beam B (the light beam for reproducing) emitted so as to track the information track TR.
The reason why the circular arc information track TR is formed as mentioned above when recording and reproducing the information by using the optical card 1 (or the optical tape) is to improve the record density of the information.
If using the optical information recording and reproducing apparatus 100 as explained above, it is possible to record the information with a high record density on the optical card 1 (or the optical tape) and further reproduce the recorded information to thereby perform the recording and reproducing operation for a large amount of the information, which uses the optical card and is superior in the compactness of the hardware (for further information, refer to "Super Large Capacity Of Optical Tape Record" and "VIEW" edited by NHK, Vol. 13, No. 1 (1994) and the like).
On the other hand, as another example of the optical information recording and reproducing apparatus using the optical card, there is an optical information recording and reproducing apparatus, in which a plurality of straight information tracks are formed in parallel to each other on the optical card, and the light beam is emitted to one of the information tracks while the optical card is being moved in parallel to the information track, and thereby the information is recorded and reproduced (a so-called "reciprocating type" of an optical information recording and reproducing apparatus). In the reciprocating type, when the recording and reproducing operation of the information is ended for one of the information tracks, an optical pickup for emitting the light beam is moved in the direction perpendicular to the information track, and then the recording and reproducing operation of the information is performed for a next adjacent information track.
When recording and reproducing the information by using the optical beam in any of the above mentioned cases, it is necessary to perform a so-called tracking control in which the light beam is emitted so as to track the information track formed on the record surface. As a method used in the recording and reproducing operation of the optical record medium for the tracking control, for example, a so-called three-beam method or a push-pull method is used, in which an objective lens is driven in a tracking direction to thereby cause a light beam to track the information track.
In the optical information recording and reproducing apparatus 100 shown in FIG. 11, for example, when considering a case of reproducing the information recorded on the information tracks TR of the optical card 1 (or the optical tape), as shown in FIG. 12A, if a straight line connecting the centers of the respective information tracks TR (each of which has a circular arc shape) and a locus of a central axis of a rotation of the rotatable optical system 104 (i.e. the locus of the central axis on the optical card 1 (or the optical tape) associated with a movement of the optical card 1 (or the optical tape)) are parallel to each other with an eccentricity shown in FIG. 12A, the locus of the light beam B associated with the rotation of the rotatable optical system 104 is displaced or shifted with respect to each of the information tracks TR.
As shown in FIG. 12B, even if the relation between the straight line connecting the centers of the respective circular arc information tracks TR and the locus of the central axis of the rotation of the rotatable optical system 104 is not parallel to each other, the locus of the light beam B associated with the rotation of the rotatable optical system 104 is displaced or shifted with respect to each of the information tracks TR.
In this way, the above mentioned tracking control is required for these cases. However, for example, a tracking displacement at the end of one information track TR may be larger than that at the center thereof, as shown in FIG. 12A, and there may be such a case that thee tracking displacement cannot be compensated only by driving the objective lens 101 in the tracking direction.
Moreover, in the reciprocating type of the optical information recording and reproducing apparatus, for example, if the optical card is placed obliquely to a moving direction thereof and then the information is recorded and reproduced, the tracking displacement at the end of the one straight information track may be larger than that at the center thereof, and there may be also such a case that the tracking displacement cannot be compensated only be driving the objective lens contained in the pickup in the tracking direction.
When the tracking displacement cannot be compensated only be driving the objective lens in the tracking direction as mentioned above, the tracking displacement may be compensated by moving the optical pickup portion itself, which emits the light beam, in the radial direction (i.e. the tracking direction) of the optical disk. However, in the optical information recording and reproducing apparatus 100 shown in FIG. 11, the directions in which the tracking displacements are compensated (the tracking directions) are different at the respective portions of one information track TR (refer to arrows in FIG. 12A). Thus, in order to move the rotatable optical system 104 to the tracking direction so as to compensate the tracking displacement, there are necessary a complex hardware structure and a complex control to move the rotatable optical system 104 in various directions corresponding to the rotation thereof. This results in a problem that the above mentioned hardware structure and control are actually nearly impossible.
Similarly in the reciprocating type of the optical information recording and reproducing apparatus, the distances in which the tracking displacements are compensated are also different at the respective portions of one information track TR. Thus, in order to move the pickup to the tracking direction so as to compensate the tracking displacement, there is also a problem that the complex hardware structure and control are required.